1. Field of the Invention
This invention relates generally to handling of substrates and, in particular, to a multi-positional, rotatable/large substrate backstop guide for a tray that holds substrates of different widths and lengths for feeding within a printing machine.
2. Description of Related Art
In a typical printer/copier, one or more suitable trays for supporting stacks of substrates or sheets are provided with the sheets being fed, in seriatim, therefrom. These trays rely on guides prior to feeding to align the sheets and may include side and rear guides adapted to engage the side edge portion and rear edge portion of a sheet stack. Usually, a pair of sheet guides is provided for locating and retaining the sheets in predetermined feeding position normal to the direction of sheet feed. A sheet stop locates the sheets in the sheet feeding direction.
For example, a tray adapted to support a stack of sheets is shown in U.S. Pat. No. 4,607,834 issued Aug. 26, 1986 to Richard M. Dastin that is adjustable to accommodate stacks of sheet material of different widths and lengths. The rear registration and the side registration surfaces are moved in unison with one another so as to engage the rear and side edges of the stack of sheet material respectively.
In FIGS. 4 and 5 of U.S. Pat. No. 4,505,575 to Stephen A. J. Palumbo, issued Mar. 19, 1985 main and auxiliary paper trays are disclosed that include a movable sheet elevator or base onto which a stack-like supply of copy sheets may be placed for use by a copier or printer. A pair of movable sheet guides is provided for locating and retaining the copy sheets in a predetermined feeding position normal to the direction of sheet feed. A fixed stop member is located in the rear of each paper tray in order to locate the copy sheets in the sheet feeding direction.
A self-centering adjustable feed tray assembly is disclosed in U.S. Pat. No. 5,332,209 issued Jul. 26, 1994 that includes a pair of edge guides opposedly arranged about the centerline of the tray. Movement of one of the edge guides results in the corresponding movement of the other about the centerline. With the use of a clutch disc, either paper guide may be moved independently of the other effectively changing the centerline relative to the feed path of a transport.
Even though the above-mentioned adjustable substrate trays are useful, there is still a need for a tray that can supply edge support near the back edge of large sheet stacks, for example, 11xe2x80x3xc3x9717xe2x80x3 or larger in order to prevent the trail edge of large size substrates from rotating while the tray is being closed with too much force. Rotation of the substrates would cause their lead edges to be skewed, giving a higher probability of a substrate jam. The conventional edge guide does not extend back far enough to provide support in this area. Typically, this edge support function is attempted by using a fixed support which can only accommodate two paper sizes (11xe2x80x3xc3x9717xe2x80x3 and A3) or a sliding guide that is difficult to access. However, the rear guide cannot be made wider to support wider substrates such as 11xe2x80x3, A3, 12xe2x80x3 and 12.6xe2x80x3 because of close proximity to another assembly within a copier/printer. A molded stop feature is not feasible because 12xe2x80x3 and 12.6xe2x80x3 wide substrates have a larger width/length ratio.
Accordingly, pursuant to the features of the present invention, an improved substrate feed tray is disclosed that answers the above-mentioned problems by providing a tall backstop guide that is attached to the bottom of the feed tray and which rotates about a vertical axis into three positions 45xc2x0 apart, presenting a different surface to a stack of substrates in the tray in each of two positions and two different surfaces to a stack of substrates in a third of the three positions of the backstop guide. Each surface accommodates a different substrate size and thereby accommodates four different widths of substrates. The backstop guide includes a cam member that is positioned in close proximity to a back wall of the tray and is adapted to be flexed into the back wall of the tray when a load is applied to the backstop guide by the stack of substrates shifting inboard due to excessive tray closing force being applied to the tray by an operator. Thus, the excess force will be transmitted to the tray""s back wall. Also, by rotating instead of sliding, the backstop guide of the present invention makes it easy to change positions with no binding, and is easy to access and manipulate by grasping the top of the guide.
These and other features and advantages of the invention are described in or apparent from the following detailed description of the exemplary embodiments.